Copolymers of isobutylene and diolefins are known and have been widely reported in the prior art. Typically, polymerization processes in which olefinically unsaturated hydrocarbons or mixtures of olefinically unsaturated hydrocarbons are polymerized use Lewis acid-type catalysts. One widely used Lewis acid-type catalyst is an aluminum halide such as aluminum chloride which may be used alone or in the form of a highly active complex with a hydrogen halide such as a hydrogen chloride in an aromatic hydrocarbon such as toluene.
Low molecular weight copolymers of isobutylene and isoprene, of a number average molecular weight of 1000 to 50,000, are taught in U.S. Pat. No. 3,766,155 (Matsushima). Isoolefins taught include isobutylene, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene, 4-methyl-1-pentene, and mixtures thereof as well as styrene, alphamethylstyrene and the like. Examples of multiolefins reacted with isoolefins include isoprene, 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, piperylene, cyclopentadiene, divinylbenzene, cyclohexadiene and the like. The polymerization temperature is generally below 0.degree. C.. The catalyst is a metal organic amide and boron trifluoride.
Other processes for preparation of low molecular weight copolymers of isoprene and isobutylene are known. U.S. Pat. No. 3,562,804 (Powers) teaches a process for preparing low bulk viscosity mastic compositions of isobutylene and isoprene in the presence of a catalyst system comprising an ethyl aluminum dichloride with a halogenated organic promoter, preferably benzyl chloride. Polymerization temperatures range from -30.degree. C. to -80.degree. C. Molecular weights obtained range from 7000 to 81,000, viscosity average molecular weight. The products of this process are characterized by a relatively low degree of unsaturation and find utility in coated and molded articles, mastics, sealants, caulking compounds, etc. Useful polymer compositions of this process include butyl rubber, a high molecular weight solid polymer.
U.S. Pat. No. 3,810/952 (Durand) teaches a method to prepare liquid copolymers of 1,3-butadiene with one or more 1-monoolefins with a high content of unsaturation. The unsaturation is taught as being as high as 96% of the total number of monomeric units which consist of cis-1,4-butadiene units. Average molecular weight by number is less than 40,000 and, in most cases, from 1000 to 5000. The catalyst is a nickel fluorocarboxylate halide. The products are useful as plasticizers, as siccative agents in coatings, as additives for adhesive compositions and as additives for lubricating oils.
A degree of unsaturation greater than 100%, it is to be noted, while desirable for many of the above applications was not attainable by the process of U.S. Pat. No. 3,810,952.
U.S. Pat. No. 4,076,926 (Milner) teaches a method for polymerization of unsaturated compounds wherein the catalyst used is an aluminum trihalide in conjunction with an alcohol or ether. In the absence of the alcohol or ether, a quantity of an undesirable insoluble gel precipitates in the polymerization reactor. Polymerization temperature is in the range of -100.degree. to +200.degree. C., more preferably from 50.degree. C. to 150.degree. C.
Accordingly, despite the desirability of obtaining a copolymer with a degree of unsaturation greater than 100% (see U.S. Pat. 3,810,952) and a copolymer of average molecular weight range of from 400 to 10,000, preferably from 400 to 5000, more preferably from 400 to 1200, suitable for use in polyesters, polyurethanes, polyamines, polyamides, and epoxy resins, the prior art does not disclose a process for preparation of a copolymer with a degree of unsaturation greater than 100%. More than one functional group is required if the resulting copolymer is not to act as an end cap or chain terminator in a specific polymerization in preparation of polyurethanes, polyesters, polyamines and other polymers.